Wednesday, February 29, 2012

Wide Tires Can Be Bad!

As more power is added to our cars, we naturally look for more rear traction.  Wider rubber with wider wheels becomes the natural solution.  Ensuring you have good clearance is important as you can rub many different parts on your car, including:

  • Fenders
  • Wheel well liners
  • Wishbones
  • Suspension
  • Chassis
Remember your tire (maybe even you wheel!) can flex under heavy cornering loads.  This reduces your clearance so it is critical that you leave room.  

The picture above shows a Nitron race shock that has a remote reservoir attached by a hose.  This joint can come in contact with an improperly sized wheel/tire combination.  

Recently we learned that a Lotus owner knocked this hose loose and lost his shock performance at the track.  He blamed the clip that holds the hose fitting to the shock.  We've never had any failure from this design but recognize that if something rubs it - like a tire - it could come loose.  Frankly, we think properly sizing your tire is the correct solution.

Recent track testing of our ETHOS 17x9 with 245 Hoosiers revealed that we were rubbing the outside fender.  Adding ReVerie rear fender flares would resolve this completely.  We will be adding these fenders soon to test but for now, we would admonish all y'all to watch clearance when adding wider wheels or tires to your Lotus!

Tuesday, February 28, 2012

Wheel Offsets and You

Wheel Offset is the relationship of the wheel center line to the mounting flange of the wheel, as seen in the picture below.

Manufacturers determine offsets by taking several aspects into consideration; such as:

  • Fitment - the given space of the wheel well during all conditions of wheel movement; whether that be the up and down motion of the suspension or the turning of the front wheel during steering.
  • Styling - cars just look better with the wheels somewhat flush with the outer fender line of the wheel well.
  • Performance - cars have a tendency to handle better with the wheels pushed out away from the center line of the vehicle.
The Lotus & Ariel have positive offset wheels with wheel bolt spacing that is unusual.  Spoke clearance from the caliper is a challenge with both of these cars as they use opposed piston calipers.  We developed many different wheels for these cars and generally have found that reducing the offset - which pushes the wheels outwards, has helped handling. Generally pushing your wheels out by 5mm works well on these cars.  

Tuesday, February 14, 2012

Don't strip it!

The undertray and diffuser are parts on our vehicles that need to come off a lot; whether that be for making repairs or just to check for leaks, tears etc. However, the stock undertray bolts can make this a real pain.

The stock undertray bolts are button-head alleys which can strip. The problem usually stems from improper use.  An allen head bolt starts to strip from overtighting them, or not putting the allen key all the way inside the head of the allen bolt. (This goes for all allen heads. Not just the undertray and diffusers. Allens are used alot on these cars, so pay attention that your key is all the way in when removing and be careful not to over-tighten.)  Conversely, if you do not remove your undertray much, the bolts start to seize inside the hole, due to rust.

One of the easiest ways to get them out, without drilling, is to get a cutoff wheel and cut a straight line through the head of the bolt. Use a punch and hammer, and tap the bolt in the direction to loosen it. You can try to use heat, but the undertrays are very sensitive to torches due to the material and the fact that it's so thin.

The easiest way to avoid all of this: replace the button heads with a standard hex head and add a little Anti-seize. You can purchase these bolts at any hardware store (M8-1.25x25 for both the undertray and diffuser). The only way to strip these bolts is by using the wrong size tool. Even if these do seize in the hole, they will come out with a standard wrench.
Highlighted in red are two of the bolts and where they should be replaced.
Working on these cars for as long as I have, and repeatedly seeing this issue, I started to change these bolts on any service, or, any time i had to remove the undertray or diffuser.

Here's a chart that is a great guide for torque specs.

Thursday, February 2, 2012

Have you inspected your MAF lately?

Modern Fuel Injection engines require the measurement of the air into the engine.
The common Mass Air Flow sensors available include:
  • Hot Wire
  • Vane Type
  • Hot Film
  • Karmen Vortex 
  • Speed Density
 The MAF found on the Lotus is of the Hot Wire type.

   Most common hot-wire MAF sensors use a platinum wire or filament heated to a prescribed, maintained temperature above ambient, located centrally in the incoming air stream. These sensors function on the electrical principle that resistance decreases with temperature. As intake air moves past the wire or film, the cooling effect causes a measurable drop in resistance, and thus lower voltage is required to maintain the prescribed temperature. The hot-wire MAF control unit is sent a reference voltage of 5V, and returns about .4V to.5V at idle and from 4.5V to 5V at full throttle. Based on a fixed data set, an accurate assumption of air mass is made. 

  However, when these sensors become contaminated, they can send false readings to the Engine Management system and cause driveability issues. 

Cleaning these sensors is quite easy and can restore performance to your engine. You will need Mass Airflow Sensor cleaner. Do not use anything other than this, as other cleaners (ie. Brake or Carb Cleaner) can leave residue on you sensor

After cleaning, you should not see any dirt and that the wires are clean.